The disclosure relates to turbine engine fan cases. More particularly, the disclosure relates to mounting of and to fan cases.
A gas turbine engine can include a fan section containing fan blades surrounded by a fan case within an aerodynamic nacelle. A function of the fan case is to contain fractured and separated parts of the fan blades, preventing any portions from leaving the fan nacelle. Metallic fan cases can be undesirably heavy to perform this containment function. A composite fan case constructed of non-metallic materials can reduce weight and provide the same containment capability as a metallic fan case.
The fan case may be mounted to a core of the engine via an array of fan exit guide vanes (FEGV). The fan case may also be mounted to a pylon of the aircraft. Additionally, a structural portion of the case may carry a liner for closely accommodating the fan blades. The liner may be configured to have different thermal expansion than the composite structural portion of the fan case. The difference allows the liner to closely accommodate the fan across a range of operating conditions.
US Patent Application Publication 2013-0195635-A1, published Aug. 1, 2013 “Fan Case Rub System”, US Patent Application Publication 2013-0195605-A1, published Aug. 1, 2013 “Fan Case Rub System, Components, and Their Manufacture”, and US Patent Application Publication 2012-0099975-A1, published Apr. 26, 2012 “Fan Case and Mount Ring Snap Fit Assembly” disclose composite fan cases for turbofan engines. Some such cases feature fiberglass layers in the composite layup (e.g., atop carbon fiber layers) along mounting surfaces (e.g., for mounting the fan case to an engine mount (e.g., a front mount of a pylon with a rear mount of the pylon engaging a core case) or a fan exit guide vane (FEGV) array or mounting the liner to the fan case).
In several examples, a metallic mount ring encircles a rear portion of the composite in an interference fit. Outer shrouds of the vanes of the FEGV array are radially inboard thereof and may be secured through the composite to the mount ring. In such situations, fiberglass layers inboard and outboard may serve to galvanically isolate the structural carbon fiber material from the metallic components. The buildup of fiberglass may also provide a margin for machining an otherwise imprecise composite to precise dimensions.
Similarly, such composite cases may include liner mounting features. One example involves a forward radially outwardly protruding flange to which a liner carrier may be mounted or to which a forward portion of the nacelle may be mounted. Again, one or both faces of the flange may be formed by fiberglass layers of the composite layup sandwiching the core structural carbon fiber material.